In 1800, lithium, in particular LiCO3, was first used to dissolve bladder stones for the treatment of urate imbalances. In 1871, there marked the first recorded use of lithium for the treatment of mania. In 1886, there was recorded use of lithium carbonate (the active ingredient in the current pill form of lithium) to prevent depression. In 1929, lithium citrate was used in “Bib-Label Lithiated Lemon-Lime Soda”, a beverage marketed as a cure for hangovers. In 1948, lithium was first used by psychiatrists to treat patients with mania, and in that same year, lithium citrate was removed from the beverage 7UP®. The following year marked lithium's first legitimate medical application, and in 1970 the FDA approved lithium for the treatment of mania. (http://www.psycheducation.org/depression/-meds/LithiumHistory.htm; Gielen, Marcel, Edward R. T. Tiekink (2005). Metallotherapeutic drugs and metal-based diagnostic agents: The use of metals in medicine. John Wiley and Sons. p. 3. ISBN 0-470-86403-6; and Gerhard N. Schrauzer. Journal of the American College of Nutrition, Vol. 21, No. 1, 14-21 (2002)).
Lithium salts have a long history of human consumption beginning in the 1800s. In psychiatry, they have been used to treat mania and as a prophylactic for depression since the mid 20th century (Shorter E. The history of lithium therapy. Bipolar Disord. 2009; 11 Suppl 2:4-9). Today, lithium salts are used as a mood stabilizer for the treatment of bipolar disorder. Although the FDA has approved no medications as safe and effective treatments for suicidality, lithium has also proven to be the only drug that consistently reduces suicidality in patients with neuropsychiatric disorders (Baldessarini R J, Tondo L, Hennen J. Treating the suicidal patient with bipolar disorder. Reducing suicide risk with lithium. Ann N Y Acad Sci. 2001; 932:24-38; discussion 9-43; Goodwin F K, Fireman B, Simon G E, Hunkeler E M, Lee J, Revicki D. Suicide risk in bipolar disorder during treatment with lithium and divalproex. JAMA. 2003; 290:1467-73).
Although suicide and suicidality are major and growing public health problems and suicide is now ranked as the 11th leading cause of death in the U.S., the relationship between psychiatric medication and suicidality has not been well studied. This is at a time when there is growing evidence that vulnerability to suicidality may be inherited independently of vulnerability to mood disorders. These considerations have led to increasing calls for a separate category for “Suicide Disorders” in DSM V. However, there is growing evidence that treatments that are effective for mood disorders are not always effective for suicidality and vice versa. Paradoxically, antidepressants, although they improve depression over 4 to 8 weeks, are not believed to lower suicidality. In contrast, lithium does appear to lower suicidality in both recurrent unipolar major depressive disorder and in bipolar depression but is not a good short-term treatment of depression. To date, no medication has been specifically approved by the US Food and Drug Administration (FDA) or by any of the world's regulatory agencies. Moreover, in the context of growing concern about suicide in the U.S., the FDA is has recently expressed interest in reviewing any medication that might demonstrate efficacy against suicidality if suicidality is the a-priori primary outcome measure. Lithium is the only medication that consistently reduces suicidality in recurrent unipolar major depressive disorder and in bipolar disorder. However existing lithium drugs such as lithium chloride and lithium carbonate suffer from chronic toxicity, poor physicochemical properties and poor brain bioavailability.
Despite these effective medicinal uses, current lithium pharmaceutics (lithium carbonate and lithium citrate) are plagued with a narrow therapeutic window that requires constant blood draws for the patient and monitoring of plasma lithium levels and thyroid hormones by a clinician. Many patients undergoing lithium therapy find the side effects to be unbearable, which negatively effects compliance and discourages physicians from utilizing lithium. These problems arise because the site of action for the treatment of psychiatric and neurodegenerative diseases are in the brain and lithium salts cross the blood-brain-barrier slowly (Davenport V D. Distribution of parenterally administered lithium in plasma, brain and muscle of rats. Am J Physiol. 1950; 163:633-41; Ebadi M S, Simmons V J, Hendrickson M J, Lacy P S. Pharmacokinetics of lithium and its regional distribution in rat brain. Eur J Pharmacol. 1974; 27:324-9). This often requires multiple administrations throughout the day to reach therapeutic concentrations. Unfortunately, this leads to peripheral accumulation of lithium resulting in metabolic adverse effects such as hypothyroidism, hyperparathyroidism, weight gain, and nephrogenic diabetes insipidus (Livingstone C, Rampes H. Lithium: a review of its metabolic adverse effects. J Psychopharmacol. 2006; 20:347-55).
Because lithium is so effective at reducing manic episodes in patients with bipolar disorder, it is still used clinically despite its narrow therapeutic index. This has led researchers to begin to look for alternatives to lithium with similar bioactivities. The problem with this approach is that the mechanism of action remains highly debated. However, recent studies have identified many important bioactivities of lithium that may be responsible for its therapeutic efficacy in its current FDA approved indications and beyond. Lithium exerts neuroprotective effects by increasing the phosphorylation of ERK (Pardo R, Andreolotti A G, Ramos B, Picatoste F, Claro E. Opposed effects of lithium on the MEK-ERK pathway in neural cells: inhibition in astrocytes and stimulation in neurons by GSK3 independent mechanisms. J Neurochem. 2003; 87:417-26). The extracellular signal-regulated kinase (ERK) pathway is important for mediating neurogenesis and synaptic plasticity and has been implicated as an important target for mood stabilizers (Chen G, Manji H K. The extracellular signal-regulated kinase pathway: an emerging promising target for mood stabilizers. Current opinion in psychiatry. 2006; 19:313-23). Lithium has also been found to inhibit enzymes that require metal ions for catalysis in a noncompetitive manner by displacing a divalent cation (Phiel C J, Klein P S. Molecular targets of lithium action. Annu Rev Pharmacol Toxicol. 2001; 41:789-813). Two of these enzymes that have important implications in bipolar disorder are glycogen synthase kinase-3 (GSK-3) and inositol monophosphatase. GSK-3 beta was first identified as the molecular target of lithium by Klein et al (Klein P S, Melton D A. A molecular mechanism for the effect of lithium on development. Proc Natl Acad Sci USA. 1996; 93:8455-9). It functions by phosphorylating glycogen synthase, the rate-limiting enzyme of glycogen biosynthesis (Alon L T, Pietrokovski S, Barkan S, Avrahami L, Kaidanovich-Beilin O, Woodgett J R, et al. Selective loss of glycogen synthase kinase-3alpha in birds reveals distinct roles for GSK-3 isozymes in tau phosphorylation. FEBS Lett. 2011; 585:1158-62). GSK-3 inhibitors like lithium generally produce a weak anti-depressant-like and strong anti-mania-like effect, which explains its utility in bipolar disorder (Rowe M K, Wiest C, Chuang D M. GSK-3 is a viable potential target for therapeutic intervention in bipolar disorder. Neurosci Biobehav Rev. 2007; 31:920-31). GSK-3 is expressed in all tissues, with particularly abundant levels in the brain (Yao H B, Shaw P C, Wong C C, Wan D C. Expression of glycogen synthase kinase-3 isoforms in mouse tissues and their transcription in the brain. J Chem Neuroanat. 2002; 23:291-7). Therefore, this enzyme has tremendous potential as a therapeutic target for the treatment of neurological diseases that are characterized by dysregulated GSK-3 such as Alzheimer's disease (AD) and HIV associated neurocognitive disorders (Anthony I C, Norrby K E, Dingwall T, Carnie F W, Millar T, Arango J C, et al. Predisposition to accelerated Alzheimer-related changes in the brains of human immunodeficiency virus negative opiate abusers. Brain. 2010; 133:3685-98; Avila J, Hernandez F. GSK-3 inhibitors for Alzheimer's disease. Expert Rev Neurother. 2007; 7:1527-33; Martinez A, Perez D I. GSK-3 inhibitors: a ray of hope for the treatment of Alzheimer's disease? J Alzheimers Dis. 2008; 15:181-91; Dewhurst S, Maggirwar S B, Schifitto G, Gendelman H E, Gelbard H A. Glycogen synthase kinase 3 beta (GSK-3 beta) as a therapeutic target in neuroAIDS. J Neuroimmune Pharmacol. 2007; 2:93-6).
In addition to inhibiting GSK-3, lithium also inhibits inositol monophosphatase (IMPase) leading to cerebral inositol depletion (Allison J H, Stewart M A. Reduced brain inositol in lithium-treated rats. Nature: New biology. 1971; 233:267-8). This has been gaining favor from some as the putative target of lithium therapy since its mechanism was elucidated by Pollack et al (Pollack S J, Atack J R, Knowles M R, McAllister G, Ragan C I, Baker R, et al. Mechanism of inositol monophosphatase, the putative target of lithium therapy. Proc Natl Acad Sci USA. 1994; 91:5766-70). Furthermore, lithium, valproic acid, and carbamazepine, which are all used for stabilization of mood, have been shown to lead to the depletion of inositol (Harwood A J. Lithium and bipolar mood disorder: the inositol-depletion hypothesis revisited. Mol Psychiatry. 2005; 10:117-26). This has bolstered support for the inositol depletion hypothesis of lithium therapy and has highlighted this molecular target in the search for “lithium mimetics” (Singh N, Halliday A C, Thomas J M, Kuznetsova O V, Baldwin R, Woon E C, et al. A safe lithium mimetic for bipolar disorder. Nature communications. 2013; 4:1332). However, given the frequency of suicidality as a comorbidity in patients with bipolar disorder (Goodwin F K, Jamison K R. Manic-depressive illness. New York: Oxford University Press; 1990; Kilbane E J, Gokbayrak N S, Galynker I, Cohen L, Tross S. A review of panic and suicide in bipolar disorder: does comorbidity increase risk? Journal of affective disorders. 2009; 115:1-10) and that only lithium consistently reduces suicidality in these patients, it is doubtful that alternate IMPase inhibitors will produce the desired clinical outcome that can be achieved with lithium.
Crystal engineering is the understanding of intermolecular interactions in the context of crystal packing and utilization of such understanding in the design of new solids with desired physical and chemical properties. Cocrystals are solids that are crystalline single phase materials composed of two or more different molecular and/or ionic compounds (i.e. cocrystal formers) generally in a stoichiometric ratio. When one or both of the cocrystal formers are ionic (i.e., salts), the resulting cocrystal is an ionic cocrystal; when both of the cocrystal formers are molecular (i.e., molecules including zwitterionic molecules), the resulting cocrystal is a molecular cocrystal. A pharmaceutical cocrystal is a cocrystal in which a pharmaceutically acceptable cocrystal former forms a supramolecular synthon with an active pharmaceutical ingredient (“API”) (Vishweshwar, P; McMahon, J. A.; Bis, J. A.; Zaworotko, M. J. “Pharmaceutical Co-Crystals.” J. Pharmaceutical Sciences, Vol. 95, No. 3, 499-516, 2006). For example, Hoogsteen's cocrystal is the combination of 1-methylthymine (MTH) and 9-methyladenine (MAD) to form MTHMAD (Schmidt, J.; Snipes, W. Int. J. Radiat. Biol., 1967, 13, 101-109; K. Hoogsteen, 1963, Acta Crystallogr., 16, 907). Crystal forms are important to pharmaceutical science for their purity, processability, physiochemical properties, stability, reproducibility, and cost of delivery. Hundreds of cocrystal forms may exist for an active pharmaceutical ingredient and it may therefore be possible to exert control over solubility to attenuate serum concentration and increase bioavailability (Smith, A. J.; Kavuru, P.; Wojtas, L.; Zaworotko, M. J.; Shytle, R. D. “Cocrystals of Quercetin with Improved Solubility and Oral Bioavailability.” Molecular Pharmaceutics, 8, 1867-1876, 2011).
Lithium remains widely prescribed by clinicians because of its efficacy and limited side effects despite its narrow therapeutic index (Halford, Bethany. “Limits of Lithium.” Chemical and Engineering News, Vol. 91, Issue 12, 15-20, 2013). Plasma levels of lithium last for 12-24 hours depending on dosage, and typically there is no trace of LiCl in the plasma at 48 hours. Lithium influx into the brain is slow, with brain levels peaking at 24 hours following single oral dose. Constant plasma levels are required for more than 24 hours to equilibrate with plasma. The proposed mechanism of action of lithium and the mechanism of inhibitory regulation of GSK-3 activity by lithium have been described. (Chiu and Chuang (2010) Molecular actions and therapeutic potential of lithium in preclinical and clinical studies of CNS disorders. Pharmacol Ther.; 128(2): 281-304). Inhibitory regulation of GSK-3 activity by lithium is affected by magnesium (Ryves, Jonathan, et al., Lithium Inhibits Glycogen Synthase Kinase-3 by Competition for Magnesium, Biochemical and Biophysical Research Communications 280, 720-725 (2001)).
Ionic cocrystals of lithium salts with compounds known to be actively transported into the cerebrospinal compartment could preferentially distribute lithium to the brain. Ionic cocrystals of NaCl and sucrose were isolated in the late 1940s (Beevers, C. A., Cochran, W. Nature. 1946, 157, 872). However, the field is relatively unexplored, and medicinal uses have not been addressed in the prior art. The prior art has also seen ionic cocrystals formed from alkali metal bromides with barbituric acid (D. Braga et al., Chem. Commun., 2010, 46, 7715-7717; Cryst. Growth Des., 2011, 11, 5621-5627; Chem. Commun., 2012, 48, 8219-8221). This and all other referenced publications are incorporated herein by reference in their entireties. Furthermore, where a definition or use of a term in a reference, which is incorporated by reference herein is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.